Known in the art are mesomorphic materials with a positive dielectric anisotropy /.DELTA..epsilon./ among which most advantageous are considered the materials consisting of substituted p-cyanobiphenyls or mixtures of substituted p-cyanobiphenyls with p-cyanoterphenyl (cf. French Pat. No. 2,207,758 Int. Cl. C 09 K 3/34, published June 21, 1974). A number of such materials are produced by a British company BDH under trade names E3, E8, etc. These materials have a wide temperature range of existence of nematic mesophase and an average value of a positive dielectric anisotropy. Thus, the material E8 passes into the nematic state at the temperature (T.sub.C-N)=-12.degree. C., and into the isotropic state--at the temperature (T.sub.N-I)=70.5.degree. C.; .DELTA..epsilon. of the material is equal to +13. However, these known mesomorphic materials have an insufficiently low value of an optical anisotropy /.DELTA.n/ which amounts, in their case, to about 0.2.
In order to lower the value .DELTA.n of the materials, it has been suggested to make use of partly hydrogenated cyanobiphenyls and terphenyls, respectively derivatives of phenyltranscyclohexane and biphenyltranscyclohexane (Angew.Chemie; Bd.89, Nr. 2, published January 1977. Verlag Chemie GMBH Weinheim/Borgstr; R. Eidenschink, D. Erdmann, J. Krause, L. Pohl "Substituierte Phenylcyclohexaneline neue Klasse flussigkristalliner Verbindungen).
Each of the above-mentioned compounds simultaneously possesses a positive dielectric anisotropy and a lowered value of optical anisotropy. Thus, a FRG company Merk produces a material consisting of the above-indicated compounds available under the trademark Nematic Phase 1132 TNC which has the following characteristics: T.sub.K-N =-6.degree., T.sub.N-I =70.degree. C.; .DELTA..epsilon.=+10.3; .DELTA.n=+0.14.
This material also features an insufficiently low value of .DELTA.n so that variation of the value of .DELTA.n vs. composition is substantially impossible. This material is produced by intermixing the components, each imparting both properties to the material: dielectric anisotropy and optical anisotropy. The resulting mixture is heated under stirring till the mixture is converted into an isotropic liquid, whereafter it is cooled to room temperature.